EP0627773B1 - Fil supraconducteur d'oxyde et appareil supraconducteur utilisant ce fil - Google Patents

Fil supraconducteur d'oxyde et appareil supraconducteur utilisant ce fil Download PDF

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EP0627773B1
EP0627773B1 EP94107489A EP94107489A EP0627773B1 EP 0627773 B1 EP0627773 B1 EP 0627773B1 EP 94107489 A EP94107489 A EP 94107489A EP 94107489 A EP94107489 A EP 94107489A EP 0627773 B1 EP0627773 B1 EP 0627773B1
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superconducting
wire
oxides
oxide
conductor
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EP0627773A1 (fr
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Kamo Tomoichi
Fukushima Keiji
Takeuchi Seizi
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Hitachi Ltd
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Hitachi Ltd
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/20—Permanent superconducting devices
    • H10N60/203—Permanent superconducting devices comprising high-Tc ceramic materials

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  • the present invention relates to superconducting wire using oxide superconductors, especially, relates to superconducting coils, superconducting current leads, and superconducting cables having preferable degree of uniformity in magnetic field and stability, and superconducting apparatus using same.
  • Oxide superconductors have been extensively investigated since the discovery of Y 1 Ba 2 Cu 3 O 7- ⁇ (M. K. Wu, J. R. Ashburn, C. T. Torng, Y. Q. Wand and C. W. Chu: Phys. Rev. Letter, 58 (1987) 908) having a critical temperature higher than a liquid nitrogen temperature with the discovery of (La/Ba) 2 Cu 1 O 4- ⁇ as a starting point, because realization of superconductor applied apparatus operable at the liquid nitrogen temperature can be expected.
  • Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ ⁇ Bi 2 Sr 2 Ca 2 Cu 3 O 10- ⁇ are superconductors having a critical temperature of about 80 K and about 105 K, respectively, (H. Maeda, Y. Tanaka, M. Fukutomi, and T. Asano: Jpn. J. Appl. Phys., 27, (1988) L209), Tl 2 Ba 2 Ca 1 Cu 2 O 8- ⁇ ⁇ Tl 2 Ba 2 Ca 2 Cu 3 O 10- ⁇ are superconductors having a critical temperature of about 110 K and about 125 K, respectively, (Z. Z. Sheng and A. M.
  • Tl 1 Sr 2 Ca 1 Cu 2 O 7- ⁇ ⁇ Tl 1 Sr 2 Ca 2 Cu 3 O 9- ⁇ are superconductors having a critical temperature of about 75 K and about 100 K, respectively, (S. Matsuda, S. Takeuchi, A. Soeta, T. Suzuki, T. Kamo: Jpn. J. Appl. Phys., 27 (1988) 2062).
  • Each of all the above superconductors has a superconducting phase having a critical temperature higher than a liquid nitrogen temperature, and since then, material development for improving characteristics of the materials have been continued in order to obtain materials having a high critical temperature, high chemical stability, and a single phase obtainable easily by synthesizing derivatives of which a part of composition is replaced with various elements.
  • gold, silver, or their alloy materials are used as the sheath material or base plate material in view of electrochemical equilibrium because the oxide superconducting material becomes partly a molten condition in a heat treatment process, shows characteristics of a caustic molten salt, and corrodes ordinary metallic conductor material such as copper-iron group.
  • gold or silver is selected as materials for sheaths and base plates in view of a chemical equilibrium.
  • gold and silver do not satisfy requirements for a practical material of wire in characteristics such as a preferable mechanical strength of the conductor, a low thermal conductivity, and a wide design selection range in electric resistance under a normal conducting state.
  • such wire is required as the one which has a characteristics as of a stabilized material with sufficiently low electric resistance as for sheath material or base plate material, and a sufficient rigidity for enduring electromagnetic force at winding the wire for forming a coil or at operation.
  • a mechanically strong current lead having a small heat absorbing property such sheath material or base plate material is required as the one which has a small thermal conductivity and a preferable mechanical strength.
  • sheath material or base plate material having a preferable high electric resistance is required.
  • a method of increasing hardness before sintering heat treatment of sheath material for an oxide superconducting wire, increasing a packed density of the superconducting powder, and increasing a critical current density of the superconducting wire after the sintering heat treatment is disclosed in JP-A-03-166 348 (1991), wherein the silver sheath material contains molybdenum oxide particles produced by internal oxidation of molybdenum particles.
  • the present invention relates to superconducting wire using oxide superconductors, and objects of the present invention are to provide sheath material and base plate material having a large mechanical strength, a low thermal conductivity, and a wide design selection range in electric resistance under a normal conducting state, composite superconducting wire therewith, and superconducting coils, superconducting current leads, permanent current switches, and superconducting cables all of which have an uniform magnetic field and a preferable stability respectively, and superconducting apparatus using thereof.
  • a composite oxide superconducting wire being composed of at least a structure having a conductor core made of an oxide superconducting material of which circumferential surface was coated with any of gold, silver or silver alloys
  • a superconducting wire having a large mechanical strength, a low thermal conductivity, and a wide design selection range in electric resistance under a normal conducting state can be obtained by composing any of the gold, the silver, or the silver alloys for coating the circumferential surface of the conductor core in a manner wherein oxides of the group as claimed in claim 1 are dispersed in the gold, the silver, or the silver alloys.
  • a wire drawing manufacturing method using a metallic sheath is taken as an example.
  • an oxide superconductor or its precursor is pulverized, and filled into a metallic pipe.
  • the metallic pipe is drawn to a wire having a designated diameter by a drawing bench or a swaging machine.
  • the above drawing process has both functions to form a designated shape of the wire and to increase a density of the pulverized oxide superconductor filled in a sheath.
  • Aimed wire can be obtained by composing a composite with at least one of the above described wire, winding the composite in a coil shape, or fabricating in a lead shape or a cable shape depending on its using object, and subsequently adding a heat treatment for crystallizing or sintering.
  • a method for forming a wire is not restricted to the above described method, but other methods such as, for example, a method for forming a tape shape wire by pressure welding of green sheets prepared on a metallic base plate by a spray-pyrolysis, a laser deposition method, a plasma spraying method, or a doctor blade method is effective. Even in this case, adding a pressing operation in the manufacturing process of wire in order to increase a critical current density of wire is preferable.
  • the sheath materials and the base plate materials used in the above described essential manufacturing process are most important subject matters of the present invention.
  • Feature of the present invention is in a structure wherein said oxide materials mentioned in claim 1 are dispersed in any of gold, silver, or their alloys, i.e. aluminum oxides, zirconium oxides, magnesium oxides, yttrium oxides, titanium oxides, and composite oxides of these compounds are said oxide materials to be dispersed.
  • the first method is a so-called mechanically alloying method wherein pulverized particles of metallic material such as gold or silver and pulverized particles of the above described oxide material are strongly mixed mechanically by a mixer such as a ball mill.
  • a so-called internal oxidation method wherein metallic elements of the oxide in metallic state are added to the gold or the silver as a precursor of the dispersed oxide, mixed mechanically, and then oxidized to form dispersed oxide, is also effective.
  • the metallic powder including the dispersed oxide obtained by the above described method is manufactured into a pipe or a plate by cold work or hot work, and are used as a sheath material or a base plate material.
  • Additive amount of the dispersed oxide varies depends on a kind of the dispersed oxide, but, a characteristics such as hardness and strength of the material is mainly determined by particle sizes and an average distance between the dispersed particles of the dispersed oxide material.
  • the average diameter of the dispersed particles is preferably utmost 1000 nm.
  • an additive amount of the oxide is taken as 1-0.1 % by weight and diameters of the dispersed oxide particles are taken as 100-20 nm, the average distance between the dispersed particles is in a range of 1000-100 nm, and aimed characteristics such as hardness and strength of the object material can be obtained.
  • a condition which makes it possible to obtain a desired electric resistance and a thermal conductivity can be determined by using the additive amount of the oxide as a parameter rather than dispersing the oxide having a smaller diameter than previous one.
  • a material is required as a preferably effective conductor having a strong mechanical strength without decreasing an electric resistance and a thermal conductivity remarkably, the requirement can be satisfied by making diameter of the additive oxide particles smaller than previous one and dispersing the particles homogeneously.
  • the sheath material has relatively small electric resistance, and accordingly, achieving a role as a stabilizer for a conventional superconducting coil can be expected.
  • superconducting materials composing superconducting wire there is no special restriction if the superconducting materials have a critical temperature higher than critical temperatures of conventional metallic or intermetallic compound superconducting wire.
  • representative oxide superconducting materials having critical temperatures higher than a liquid nitrogen temperature the following materials and their derivatives are effective; Y 1 Ba 2 Cu 3 O 7- ⁇ , Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ , Bi 2 Sr 2 Ca 2 Cu 3 O 10- ⁇ , Tl 2 Ba 2 Ca 1 Cu 2 O 8- ⁇ , Tl 2 Ba 2 Ca 2 Cu 3 O 10- ⁇ , Tl 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ , TlSr 2 Ca 2 Cu 3 O 9- ⁇
  • Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ , Bi 2 Sr 2 Ca 2 Cu 3 O 10- ⁇ , and their derivatives, or their mixtures are preferable for use.
  • a superconductor is obtained by filling the oxide superconductor powder or its precursor powder directly into an oxide dispersed silver pipe fabricated in accordance with the above described method and drawing the pipe.
  • a most simple example of the conductor structure is the one which is obtained by arranging an oxide dispersed silver sheath at outer periphery surface of a superconductor core.
  • the above example shows a single conductor structure, but the same structure can be selected easily for a multiconductor cable.
  • a structure can be suggested as the one wherein an oxide superconductor according to the present invention is used as a conductor core, a single conductor cable is manufactured by filling the conductor core into a sheath which is made of silver or a silver alloy having at least one of dispersed oxide particles selected from a group of aluminum oxides, zirconium oxides, magnesium oxides, yttrium oxides, titanium oxides, and their composite oxides such as strontium titanate and drawing the sheath to a wire, and a plurality of the single conductor cables are bundled and inserted into the above sheath further, and drawn again to a wire.
  • a conductor having the above described structure can be used.
  • a coaxial cable structure can be exemplified.
  • the coaxial cable structure having a conductor portion of oxide superconductor at center of the cross section as a core, a sheath material portion of silver or a silver alloy having at least one of dispersed oxide particles selected from a group of aluminum oxides, zirconium oxides, magnesium oxides, yttrium oxides, titanium oxides, and their composite oxides such as strontium titanate at outer periphery of the conductor portion, an insulating material layer at outer periphery of the sheath material portion, an oxide superconductor portion at outer periphery of the insulating material layer, and again the sheath material portion at outer periphery of the oxide superconductor portion, all of which are arranged in a concentric manner, can be proposed.
  • the conductor manufactured in a desired structure as explained above is fabricated, further, in a form of leads, cables, or superconducting coils, and subsequently, a heat treatment for connecting the superconductor particles so as to realize electrically strong junction is performed. It is a so-called wind-and-react method. However, when deformation of the conductor is small, for example, such as utmost 0.5 %, a so-called react-and-wind method wherein the superconductor particles are previously connected by the heat treatment, and then the conductor having electrically strong junction is fabricated in a form of leads, cables, or superconducting coils can be used. The above heat treatment is performed in order to enhance characteristics of the superconductor.
  • a condition for the heat treatment varies depending on materials, but generally, an atmosphere for the heat treatment is specified.
  • a low oxygen partial pressure condition for example 7 % O 2
  • a high oxygen partial pressure condition is preferable as a final heat treatment condition, and, for example, a pure oxygen condition is selected.
  • the present invention has a feature that the reinforced materials for the sheath relating to the present invention are hardly effected by the atmosphere of the heat treatment.
  • a conductor having a preferable large mechanical strength can be provided by using an oxide superconducting wire wherein an oxide superconducting material is used as a core, silver or a silver alloy is coated above outer periphery of the core to form a structure, and a plurality of the structure are composed to form a composite oxide superconducting wire, characterized in that the silver or the silver alloy coating material includes dispersed oxides mentioned above.
  • one of features of the present invention is a capability of selecting a sheath material having both a relatively small thermal conductivity and a small electric conductivity or a sheath material having both a relatively large thermal conductivity and a large electric conductivity by controlling particle sizes, degree of dispersion, and an amount of the oxide particles added to the silver or the silver alloy coating material.
  • a superconducting magnet is sometimes composed in a form of multiple cylinders depending on its using object. Composing the form of multiple cylinders is an effective method when a generated magnetic field strength is large. For instance, it is effective in a case when outer cylindrical coils are composed of superconductors having a relatively small upper critical magnetic field, of which manufacturing method is relatively simple or low cost, and as for inner cylindrical coils, conductors having a high upper critical magnetic field, of which manufacturing method is even if expensive or complicated, must be selected.
  • an all superconducting magnet such as the one exceeding 18 T is formed in a multiple cylindrical coils, and its inner coils can be realized by wire using Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ , or Bi 2 Sr 2 Ca 2 Cu 3 O 10- ⁇ superconductor, but, at the present, wire using silver sheaths has only insufficient mechanical strength, and can not endure an electromagnetic force added to the inner cylindrical coils.
  • silver containing about 3 % of dispersed materials such as calcia, strontia, baria, or oxides of rare earth elements having a small diameter less than 100 nm (1000 ⁇ ) for example is used as the sheath material, the sheath material is a preferably good conductor as functions as a stabilized material, and wire having a sufficient mechanical strength for enduring the electromagnetic force can be obtained.
  • a sheath material having both a sufficient mechanical strength and a small thermal conductivity is desired.
  • the apparatus When a large amount of energy is stored by charging into a superconducting coil such as a superconducting magnet energy storage apparatus (SMES), the apparatus is essentially composed of mainly a superconducting coil and a permanent switch.
  • the coil and the switch are installed sometimes in separated cryostats, respectively, on account of necessity to flow a large current even to the permanent switch.
  • less electric resistance loss at a cable connecting the superconducting coil and the switch is desired in order to decrease energy loss at storage.
  • the superconductor relating to the present invention can effectively be used.
  • silver containing materials such as calcia, strontia, baria, or oxides of rare earth elements more than 10 % in a dispersed degree to give a sufficiently low thermal conductivity can be used as a sheath material.
  • a raw material prepared by an oxalate coprecipitation method so as to be Ba 1.6 Sr 0.4 Ca 2.0 Cu 3.0 O ⁇ in a cation ratio is previously calcined in air at 650 °C for 15 hours, and subsequently the raw material is pulverized by a crusher for 30 minutes. At this time, a necessary amount of thallium oxide for making the cation ratio of the raw material to be Tl 2.0 Ba 1.6 Sr 0.4 Ca 2.0 Cu 3.0 O ⁇ is previously added to the raw material. Powder of the raw material obtained as described above is calcined in an aluminum oxides crucible with a lid in air at 750 °C for 15 hours.
  • Main component of the obtained powder was revealed as Tl 2 Ba 2 Ca 1 Cu 2 O 8- ⁇ by powder X-ray diffraction analysis.
  • the powder included a material containing Sr-Ca-Cu-O of which crystal structure was unable to be determined, CaO, SrO and others.
  • the above calcined material was again pulverized by a crusher for about 30 minutes so that its average diameter became a several micrometers, and obtained powder was used as the raw material for a superconducting wire.
  • the above raw material powder of the superconducting wire is filled in a pipe, 4.5 mm inner diameter and 6.0 mm outer diameter, one end of which is closed, made from silver wherein 10 % by weight zirconium oxide having a diameter of 80 nm (800 ⁇ ) is dispersed by a mechanical alloying method.
  • a pipe 4.5 mm inner diameter and 6.0 mm outer diameter, one end of which is closed, made from silver wherein 10 % by weight zirconium oxide having a diameter of 80 nm (800 ⁇ ) is dispersed by a mechanical alloying method.
  • an open end is closed, and the pipe is drawn to a wire by a drawing bench with a drafting ratio of about 20 %.
  • the worked pipe is annealed in air at 350-400 °C after each drawing operation of two or three times drawings, and finally a wire of 0.7 mm in diameter is obtained.
  • a test piece 4 cm long is cut out from the obtained wire, and is fabricated to a flatten shape by being pressed with a pressing machine of 19.6 MPa (20 t/cm 2 ).
  • the flatten test piece is calcined in a crucible with a lid in air at 830 °C for 20 hours.
  • the obtained test piece is pressed again with the pressing machine of 19.6 MPa (20 t/cm 2 ), and calcined again in a crucible with a lid in air at 830 °C for 20 hours.
  • a structure of the obtained wire test piece is illustrated schematically in FIG. 1.
  • the oxide superconductor core 2 has a tape shape structure cladded with a silver sheath 1 containing dispersed zirconium oxide therein.
  • a critical temperature Tc and a critical current density Jc of the test piece obtained by repeating the above pressing and calcining four times were determined by a resistivity measurement using a standard four probe method at 77 K under no outer magnetic field, and it was revealed that Tc and Jc were 115 K and 30000 A/cm 2 , respectively.
  • a composition of the superconductor forming the core of the wire test piece prepared by the same method as described above was analyzed by an ICP method, and it was revealed that chemical composition of the test piece was Tl 1.68 Ba 1.58 Sr 0.41 Ca 1.98 Cu 3.0 O ⁇ .
  • a raw material powder of the wire prepared by the same method as that of the embodiment 1 was made into a wire using a silver pipe, 4.5 mm inner diameter and 6.0 mm outer diameter, including dispersed magnesium oxides particles having a crystal grain size of about 110 nm (1100 ⁇ ) by the same method as the embodiment 1. That is, after the above raw material powder is filled in the silver pipe, an open end of the pipe is closed, and the pipe is drawn to a wire by a drawing bench with a drafting ratio of about 20 %. The worked pipe is annealed in air at 350-400 °C after each drawing operation of two or three times drawings, and finally a wire of 0.7 mm in diameter is obtained.
  • a test piece 4 cm long is cut out from the obtained wire, and is fabricated to a flatten shape by being pressed with a pressing machine of 19.6 MPa (20 t/cm 2 ).
  • the flatten test piece is calcined in a crucible with a lid in air at 830 °C for 20 hours.
  • the obtained test piece is pressed again with the pressing machine of 19.6 MPa (20 t/cm 2 ), and calcined again in a crucible with a lid in air at 830 °C for 20 hours.
  • a critical temperature Tc and a critical current density Jc of the test piece obtained by repeating the above pressing and calcining four times were determined by a resistivity measurement using standard four probe method at 77 K under no outer magnetic field, and it was revealed that Tc and Jc were 113 K and 24000 A/cm 2 , respectively.
  • a composition of the superconductor forming the core of the wire test piece prepared by the same method as described above was analyzed by an ICP method, and it was revealed that chemical composition of the test piece was Tl 1.71 Ba 1.62 Sr 0.38 Ca 1.96 Cu 3.0 O ⁇ .
  • Necessary amounts of composing oxides such as SrO, CaO, and CuO for obtaining a cation ratio of Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ are mixed and pulverized by a crusher for 30 minutes.
  • the obtained mixed powder is calcined in an aluminum oxides crucible in air at 800 °C for 20 hours.
  • the obtained powder was analyzed by an X-ray diffraction analysis, and it was revealed that a main component of the powder was Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ .
  • the powder included a material containing Sr-Ca-Cu-O of which crystal structure was unable to be determined, Bi 2 Sr 2 Cu 1 O ⁇ and others.
  • the above calcined material was pulverized by a crusher for about 30 minutes so that its average diameter became a several micrometers, and obtained powder was used as the raw material for a superconducting wire.
  • the above raw material powder of the superconducting wire is filled in a pipe, 4.5 mm inner diameter and 6.0 mm outer diameter, one end of which is closed, made from silver wherein 15 % by weight aluminum oxides having a diameter of 260 nm (2600 ⁇ ) is dispersed by a mechanical alloying method.
  • a pipe 4.5 mm inner diameter and 6.0 mm outer diameter, one end of which is closed, made from silver wherein 15 % by weight aluminum oxides having a diameter of 260 nm (2600 ⁇ ) is dispersed by a mechanical alloying method.
  • an open end is closed, and the pipe is drawn to a wire by a drawing bench with a drafting ratio of about 20 %.
  • the worked pipe is annealed in air at 350-400 °C after each drawing operation of two or three times drawings, and finally a wire of 0.7 mm in diameter is obtained.
  • a test piece 4 cm long is cut out from the obtained wire, and is put into an aluminum oxides crucible.
  • the oxide superconductor Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ 2 forms a core, and wire having a circular cross sectional structure is formed with a cladding made of a silver sheath 1 containing dispersed aluminum oxides therein.
  • a critical temperature Tc and a critical current at 4.2 K of the obtained test piece were determined by a resistivity measurement using standard four probe method. It was revealed that Tc and the critical current were 84 K and 115 A, respectively.
  • a composition of the superconductor forming the core of the wire test piece prepared by the same method as described above was analyzed by an ICP method, and it was revealed that chemical composition of the test piece was Bi 1.98 Sr 2.01 Ca 0.98 Cu 2 O 8- ⁇ .
  • a raw material prepared by an oxalate coprecipitation method so as to be Ba 1.6 Sr 0.4 Ca 2.0 Cu 3.0 O ⁇ in a cation ratio is previously calcined in air at 650 °C for 15 hours, and subsequently the raw material is pulverized by a crusher for 30 minutes. At this time, a necessary amount of thallium oxide for making the cation ratio of the raw material to be Tl 2.0 Ba 1.6 Sr 0.4 Ca 2.0 Cu 3.0 O ⁇ is previously added to the raw material. Powder of the raw material obtained as described above is calcined in an aluminum oxides crucible with a lid in air at 750 °C for 15 hours.
  • Main component of the obtained powder was revealed as Tl 2 Ba 2 Ca 1 Cu 2 O 8- ⁇ by powder X-ray diffraction analysis.
  • the powder included a material containing Sr-Ca-Cu-O of which crystal structure was unable to be determined, CaO, SrO and others.
  • the above calcined material was again pulverized by a crusher for about 30 minutes so that its average diameter became a several micrometers, and obtained powder was used as the raw material for a superconducting wire.
  • the above raw material powder of the superconducting wire is filled in a pipe, 6.0 mm inner diameter and 8.0 mm outer diameter, one end of which is closed, made from silver wherein 20 % by weight zirconium oxide having a diameter of 380 nm (3800 ⁇ ) is dispersed by a mechanical alloying method.
  • a pipe 6.0 mm inner diameter and 8.0 mm outer diameter, one end of which is closed, made from silver wherein 20 % by weight zirconium oxide having a diameter of 380 nm (3800 ⁇ ) is dispersed by a mechanical alloying method.
  • an open end is closed, and the pipe is drawn to a wire by a drawing bench with a drafting ratio of about 20 %.
  • the worked pipe is annealed in air at 350-400 °C after each drawing operation of two or three times drawings, and finally a wire of 1.2 mm in diameter is obtained.
  • the obtained wire is further manufactured to a tape shape of about 0.7 mm thick and about 6 mm wide by a rolling mill having rollers of 100 mm in diameter, and 20 test pieces of 110 mm long are cut out from the tape shaped wire.
  • Each of the 20 test pieces is pressed by a pressing machine of 19.6 MPa (20 t/cm 2 ) to form a flatten shape of about 0.25 mm thick.
  • the obtained 20 flatten shape test pieces are stacked and press-welded with a pressure of about 1.96 MPa (2 t/cm 2 ) to form a rectangular cross section.
  • the obtained conductor having a rectangular cross section of about 9 mm wide and about 4.7 mm thick is annealed in air at 830 °C for 30 hours.
  • the obtained conductor is pressed again with a pressure of about 1.96 MPa (2 t/cm 2 ), and annealed in pure oxygen at 830 °C for 30 hours.
  • a cross sectional structure of the obtained conductor is illustrated schematically in FIG. 3.
  • the conductor is composed with 20 elementary wires 3 in each of which the oxide superconductor Tl 2.0 Ba 1.6 Sr 0.4 Ca 2.0 Cu 3.0 O ⁇ 2 is used as a core which is coated with a silver sheath 1 containing dispersed zirconium oxide therein.
  • Current leads made of copper mesh are respectively connected to each of both ends of the obtained conductor, and voltage terminals made of silver wire were attached at middle portion of the conductor with intervals of respective 30 mm.
  • the obtained conductor was fixed to a holder made of fiber reinforced plastic and installed in a cryostat, and a critical current was measured with cooled with liquid nitrogen. The critical current was 630 A.
  • Necessary amounts of composing oxides such as SrO, CaO, and CuO for obtaining a cation ratio of Bi 2 Sr 2 Ca 2 Cu 3 O 10- ⁇ are mixed and pulverized by a crusher for 30 minutes.
  • the obtained mixed powder is calcined in an aluminum oxides crucible in air at 790 °C for 20 hours.
  • the obtained powder was analyzed by an X-ray diffraction analysis, and it was revealed that a main component of the powder was Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ . According to an observation by a scanning electron microscope and an energy dispersive X-ray analysis, the powder included a material containing Sr-Ca-Cu-O of which crystal structure was unable to be determined, SrO and others.
  • the above calcined material was pulverized by a crusher for about 30 minutes so that its average diameter became a several micrometers, and obtained powder was used as the raw material for superconducting wire.
  • the above raw material powder of the superconducting wire is filled in a pipe, 4.5 mm inner diameter and 6.0 mm outer diameter, one end of which is closed, made from silver wherein 35 % by weight zirconium oxides having a diameter of 260 nm(2600 ⁇ ) is dispersed by a mechanical alloying method. After the filling, an open end is closed, and the pipe is drawn to a wire by a drawing bench with a drafting ratio of about 20 %.
  • the worked pipe is annealed in air at 350-400 °C after each drawing operation of two or three times drawings, and finally a wire of 1.2 mm in diameter is obtained.
  • the obtained wire is further manufactured to a tape shape of about 0.7 mm thick and about 6 mm wide by a rolling mill having a roll of 100 mm in diameter, and 20 test pieces of 110 mm long are cut out from the tape shaped wire.
  • Each of the 20 test pieces is pressed by a pressing machine of 19.6 MPa (20 t/cm 2 ) to form a flatten shape of about 0.25 mm thick.
  • the obtained 20 flatten shape test pieces are stacked and press-welded with a pressure of about 1.96 MPa (2 t/cm 2 ) to form a rectangular cross section.
  • the obtained conductor having a rectangular cross section of about 9.1 mm wide and about 4.5 mm thick is annealed in air at 800 °C for 15 hours.
  • the obtained conductor is pressed again with a pressure of about 1.96 MPa (2 t/cm 2 ), and annealed in air at 830 °C for 40 hours.
  • the obtained conductor is pressed again with a pressure of about 1.96 MPa (2 t/cm 2 ), and annealed in air at 845 °C for 40 hours.
  • the conductor obtained in the embodiment 4 was connected to a superconducting coil 6 of 1 T using a NbTi superconducting wire shown in FIG. 4 in a cryostat 4 at a portion for connecting outer power source as for an oxide superconducting current lead 10 via a lead connecting terminal 7.
  • the connecting portion of the oxide current lead and the coil is immersed in liquid helium 5, upper portion of the lead is connected with copper lead 11 at a thermal anchor 8 having an inlet for liquid nitrogen 9, and the connecting portion of the oxide current lead 10 and the copper lead 11 is cooled by liquid nitrogen.
  • the copper current lead portion has a structure which is cooled by helium gas generated in the cryostat and exhausted outside through a helium gas guide pipe.
  • Penetrating heat calibrated to that of 200 A current flows which is estimated from a generated amount of helium gas at power off was about 0.4 W/kA, and penetrating heat at actually 200 A current flows was as small as about 0.55 W/kA. It could be explained that because the oxide superconducting current lead in the cryostat operated in a superconducting condition, and resistance heat generation hardly occurred.
  • FIG. 5a illustrates an embodiment of multistructural type super strong magnetic field magnet.
  • a superconducting coil 6 is installed in a cryostat 4 cooled with liquid helium 5, and a test port 13 is provided inside of an inner coil 16.
  • a coolant inlet 12 is provided at upper portion of the cryostat, and coolant is supplied through the inlet.
  • the superconducting coil is excited by being supplied with power from outside through a current lead 11.
  • FIG 5b is a schematic illustration indicating a composition of a coil using an oxide superconducting wire relating to the present invention.
  • the superconducting coil is composed with three layers, that is, an outer layer coil 14 is a coil using NbTi alloy type superconductor, a middle layer coil is a coil 15 using (Nb/Ti) 3 Sn compound type superconductor, and an inner layer coil is a coil using a circular cross sectional superconductor prepared by the same method as that of the embodiment 3 having Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ superconductor as a core and a silver sheath containing dispersed aluminum oxides therein as a coating.
  • a critical current density of the Bi 2 Sr 2 Ca 1 Cu 2 O 8- ⁇ superconductor at a liquid helium temperature in a magnetic field exceeding 18 T is larger than that of conventional NbTi alloy type superconductor and (Nb/Ti) 3 Sn compound type superconductor, and accordingly a larger magnetic field than magnetic fields generated by the above other superconductors can be generated.
  • a conductor having preferable mechanical strength, and preferably controlled electric conductivity and thermal conductivity to arbitrary ranges corresponding to its use object can be composed.
  • an advantage in improving mechanical strength of the conductors is remarkable, and chemically stable materials can be obtained in accordance with the present invention.

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  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
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  • Inorganic Compounds Of Heavy Metals (AREA)
  • Physical Vapour Deposition (AREA)
  • Containers, Films, And Cooling For Superconductive Devices (AREA)

Claims (13)

  1. Fil supraconducteur en oxyde, comprenant
    une âme conductrice (2) en oxyde supraconducteur, et
    une gaine métallique (1) en métal conducteur, dans laquelle des oxydes métalliques non-supraconducteurs sont dispersés, formée sur le pourtour de ladite âme conductrice (2).
       caractérisé en ce que
       lesdits oxydes métalliques non-supraconducteurs comprennent au moins un oxyde choisi dans un groupe d'oxydes d'aluminium, d'oxydes de zirconium, d'oxydes de magnésium, d'oxydes d'yttrium, d'oxydes de titane et d'oxydes complexes desdits oxydes, et en ce que la résistance à la traction du fil supraconducteur en oxyde est au moins de 98,1 N/mm2 (10 kgf/mm2).
  2. Fil supraconducteur en oxyde selon la revendication 1, dans lequel
       lesdits oxydes métalliques non-supraconducteurs ont respectivement un point de fusion supérieur au point de fusion de la gaine métallique (1).
  3. Fil supraconducteur en oxyde selon la revendication 1, dans lequel
       lesdits oxydes métalliques non-supraconducteurs sont chimiquement inactifs avec l'oxyde supraconducteur constituant l'âme conductrice (2).
  4. Fil supraconducteur en oxyde selon la revendication 1, dans lequel
       les particules desdits oxydes métalliques non-supraconducteurs mesurent au maximum 1000 nm.
  5. Fil supraconducteur en oxyde selon la revendication 1, dans lequel ladite gaine métallique (1) est en argent ou en alliage d'argent.
  6. Fil supraconducteur en oxyde selon la revendication 5, dans lequel lesdites particules dispersées d'oxydes métalliques ou d'oxydes complexes mesurent en moyenne au maximum 1000 nm.
  7. Fil supraconducteur en oxyde selon la revendication 1, comprenant une pluralité de fils élémentaires ayant une âme conductrice (2) en oxyde supraconducteur, chaque fil élémentaire ayant une gaine métallique (1) en argent ou en alliage d'argent formée sur le pourtour de ladite âme conductrice (2), et
       ladite gaine métallique (1) selon la revendication 1 est formée sur le pourtour de ladite pluralité de fils élémentaires.
  8. Bobine supraconductrice, comprenant
    une âme conductrice (2) en oxyde supraconducteur, et
    un fil supraconducteur ayant une gaine (1) selon les revendications 1 et 5 formée sur le pourtour de ladite âme conductrice (2), et
    une canette pour enrouler ledit fil supraconducteur.
  9. Bobine supraconductrice composite, comprenant
    une pluralité de bobines-blocs (14, 15, 16) réalisées séparément sous une forme cylindrique coaxiale, dans lequel
    au moins une (16) desdites bobines est une âme conductrice en oxyde supraconducteur, et le pourtour de ladite âme conductrice est revêtu d'une gaine (1) selon les revendications 1 et 5.
  10. Bobine supraconductrice composite selon la revendication 9,
    dans lequel le pourtour de ladite âme conductrice est revêtu d'une gaine composite constituée d'au moins deux types de matières de gainage, et
    au moins une desdites matières de gainage est celle revendiquée dans les revendications 1 et 5.
  11. Bobine supraconductrice composite selon la revendication 10, dans laquelle
       les bobines-blocs (14, 15) autres que la bobine conductrice (16) sont en matière supraconductrice du groupe des métaux ou du groupe des composés intermétalliques.
  12. Dispositif supraconducteur, comprenant
    une bobine supraconductrice (6) en oxyde supraconducteur,
    un cryostat (4) pour refroidir ladite bobine supraconductrice (6),
    un conducteur (10) de courant pour fournir de l'extérieur de l'électricité à ladite bobine supraconductrice (6), et
    une ancre thermique (8) pour maintenir une partie spécifiée dudit conducteur (10) de courant à une température spécifiée,
    caractérisé
    en ce qu'il comporte une âme conductrice (2) composée dudit oxyde supraconducteur au niveau d'une partie située plus bas que ladite partie spécifiée dudit conducteur (10) de courant maintenu à ladite température spécifiée dans ledit cryostat (4), et
    un conducteur constitué par une gaine en matière composite (1)selon les revendications 1 et 5.
  13. Système de stockage d'énergie, comprenant
    un dispositif de stockage d'énergie comprenant une bobine supraconductrice, et
    un dispositif d'entrée/sortie d'énergie pour fournir/extraire une énergie électrique audit/dudit dispositif de stockage d'énergie,
       caractérisé par
    la formation d'une âme conductrice (2) avec un supraconducteur ayant une température critique supérieure à la température critique d'un supraconducteur utilisé dans ledit système, la formation d'un conducteur composite avec une matière de gainage en argent ou en alliages d'argent sous le pourtour de ladite âme conductrice, et
    la liaison électrique de ladite âme conductrice (2) avec ledit conducteur composite par un câble à l'aide d'un fil supraconducteur composé de ladite matière de gainage (1) selon les revendications 1 et 5.
EP94107489A 1993-05-17 1994-05-13 Fil supraconducteur d'oxyde et appareil supraconducteur utilisant ce fil Revoked EP0627773B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP114366/93 1993-05-17
JP5114366A JPH06325630A (ja) 1993-05-17 1993-05-17 酸化物超電導線材及び超電導装置

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EP0627773A1 EP0627773A1 (fr) 1994-12-07
EP0627773B1 true EP0627773B1 (fr) 1997-03-12

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EP94107489A Revoked EP0627773B1 (fr) 1993-05-17 1994-05-13 Fil supraconducteur d'oxyde et appareil supraconducteur utilisant ce fil

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EP (1) EP0627773B1 (fr)
JP (1) JPH06325630A (fr)
DE (1) DE69401992T2 (fr)

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EP0627773A1 (fr) 1994-12-07
DE69401992T2 (de) 1997-06-26
JPH06325630A (ja) 1994-11-25
DE69401992D1 (de) 1997-04-17
US5625332A (en) 1997-04-29

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